Lubricating oil additives

ABSTRACT

A new class of lubricating oil additives is provided. The class consists of cooligomers of C30-C300 hydrocarbyl-substituted succinic acids and polysecondary amines which are subsequently reacted with polyisocyanate.

United States Patent 1191 1111 3,850,826 de Vries 1 Nov. 26, 1974 [54] LUBRICATING OIL ADDITIVES 3,373,111 3/1968 Le Suer et a]. 252/515 A [75] Inventor: Louis de vries, Greenbrae, Calif. 1 3,573,205 3/1971 Lowe et al 252/515 A Assigneel 'f Research p y San Primary Examiner-Patrick P. Garvin Franclscm Cahf' Assistant ExaminerAndrew H. Metz [22] Filed: 20 1973 Attorney, Agent, or FirmG. F. Magdeburger; C. J.

Tonkin; S. R. La Paglia [2]] Appl. No.: 333,586

[57] ABSTRACT [52] US. Cl 252/515 A H 1 51 1111. C1 Cl0n 1/32 A new Class Of [ubncatmg 1 addltlves 1S P 581 Field of Search .1 252/515 A; 260/4045 The Class COHSISIS of coiillgomers of W M hydrocarbyl-substituted succinic acids and polyse- 5 References Cited conciary amines which are subsequently reacted with UNITED STATES PATENTS polysocyanate- 3,219,666 11/1965 Norman at al 250/515 A X 5 Claims, N0 Drawings LUBRICATING OIL ADDITIVES BACKGROUND OF THE INVENTION 1. Field of the Invention Lubricating oils are employed for the lubrication of moving engine parts and as a vehicle for additives which promote the protection of the metallic surfaces being lubricated. Specifically, the surfaces must be protected by the lubricating composition from rust, corrosion, and the deposition of varnish. Varnish deposition is inhibited by dispersing the varnish precursors with suitable dispersant additives, preferably ashless dispersants. Furthermore, the composition must not be prone to haze or sludge formation, or thermal and oxidative breakdown and the accumulation of corrosive oxidation products.

It is sometimes found that conventional ashless dispersants, even in overbased compositions, are unable to adequately provide rust and corrosion inhibition as well as the necessary dispersancy presently required for modern internal combustion engine lubricating oils.

2. Description of the Prior Art Certain hydrocarbyl-substituted succinimides of piperazine derivatives have been suggested as ashless dispersants additives for internal combustion engine lubricating oils, Drummond, Anderson and Stuart, US. Pat. Nos. 3,024,195 and 3,024,237, as have polypiperazine derivatives of alkenyl succinimides, Anderson and Honnen, US. Pat. No. 3,200,076.

Lowe and Hendrickson, US. Pat. No. 3,573,205, disclose lubricating compositions containing a dispersant which is the reaction product of a diisocyanate and the polyisobutenyl succinimide produced by reacting polyisobutenyl succinic acid with polyamines containing primary amino groups.

SUMMARY A new class of lubricating oil additives which function as superior ashless dispersants in internal combustion engines has been found. These additives contain cooligomers of a hydrocarbylsubstituted succinic acid. The cooligomers are formed by reacting a hydrocarbylsubstituted succinic acid, anhydride or ester wherein the hydrocarbyl is of at least 30 carbon atoms, with a polysecondary amine such as a substituted piperazine, to form a first reaction product which is a cooligomer. The cooligomer is in turn reacted with an organic polyisocyanate. The product is a superior dispersant lubricating oil additive having improved dispersancy.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a high molecular weight lubricating oil additive based on cooligomers containing hydrocarbyl-substituted succinic acid moieties connected by tert.-amide linkages. The cooligomers are subsequently reacted with a polyisocyanate. The molecular weight of the product is increased by the coupling of the cooligomers by means of the polyisocyanate. The hydrocarbyl group contains at leat about 30 and preferably less than about 300 carbon atoms. The high molecular weight additive imparts superior antivamish characteristics to the oil composition. By succinic acid is intended those succinic acid-generating compounds which reactwith secondary amine, i.e., acids, anhydrides, esters, acyl halides, etc.

The polyisocyanatedinked cooligomeric composition may be used directly as a lubricating oil dispersant, or it may be reacted with a C -C amine containing primary or secondary amino nitrogen atoms before use.

I-Iydrocarbyl, as used herein, denotes an organic radical composed of hydrogen and carbon, except for minor, sometimes adventitious, amounts of other elements such as oxygen, nitrogen, halogens, etc., which may be aliphatic, alicyclic, aromatic or combinations thereof, e.g., aralkyl. Preferably, the hydrocarbyl group will be relatively free of aliphatic unsaturation, i.e., ethylenic and acetylenic, particularly acetylenic unsaturation. The hydrocarbyl substituent will contain an average of at least 30 and preferably less than an average of 300 carbon atoms. The hydrocarbyl groups are preferably aliphatic, having preferably from 0 to 2 sites of ethylenic unsaturation and most preferably from 0 to 1 such site. Hydrocarbyl groups derived from a polyolefin, itself derived from olefins (normally l-olefins) of from 2 to 6 carbon atoms (ethylene being copolymerized with an olefin of at least 3 carbon atoms), or from a high molecular weight petroleum derived hydrocarbon, are preferred and of these, polyisobutenyl is most preferred. Illustrative sources for the high molecular weight hydrocarbyl substituents are petroleum mineral oils such as naphthenic brightstocks, polypropylene, polyisobu'tylene, poly-l-butene, copolymers of ethylene and propylene, poly-l-pentene, poly-4-methyl-lpentene, polyl -hexene, poly-3-methylbutene-l etc.

The term co'ciligomer is derived from the term oligomer as copolymer" is derived from polymer. An oligomer is a single molecule produced by linking a limited number of monomers. In general, the linking of more than 2 and less than about 30 monomers produces an oligomeric structure. The properties of the oligomer differ from those of both the monomeric mixture and the copolymer. A given coijligomeric composition will contain individual co'ciligomers which contain from about 3 to about 30 linked monomers and thus the cooligomeric molecular weight is an average molecular weight.

The polysecondary amine is required to form the 'co'o'ligome'rs of this invention to avoid the formation of imides which would serve to limit chain length. A polysecondary amine is a polyamine containing two or more secondary amino nitrogen atoms and no primary' amino nitrogen atoms. The polysecondary amines which find use in the present invention are C -C polysecondary amines containing from 2 to about 12 nitrogen atoms, preferably disecondary amines containing from 2 to 6 nitrogen atoms, and most preferably piperazine. The polysecondary amine may be substituted or unsubstituted, for example, alkylated or peralkylated, with the proviso that at least two secondary amino nitrogens remain available to form the cooligomeric structure. Such amines include, but are not limited to, piperazine, 2-methyl piperazine, 2,3-methyl ethyl piperazine, 5-tetrapropenyl-piperazine, 6-ethoxypiperazine, N,N-dimethylethylene diamine, N,N'- dimethyl diethylene triamine, and ethylene dipipera- Organic polyisocyanates react with primary or secondary amino nitrogen atoms to yield hydrocarbyl-ureas or polyureas which serve to link together the cooligomers into high molecular weight materials which are superior dispersants. Examples of such organic polyisocyanates include phenylene diisocyanate, toluene diisocyanate, methylene phenyl diisocyanate, hexamethylene diisocyanate, and polymeric isocyanates, such as polymethylene-polyphenyl-isocyanate. In general, the organic isocyanate coupling agent will be an aryl, alkyl or alkaryl diisocyanate, characterized by molecular weights below about 400. Polysecondary amines and polyisocyanates which find use in the present invention are reagents known to the art (Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. II, page 99f, and Vol. XII, page 45f, 2nd Ed., Interscience Publishers, New York, 1963). Useful organic polyisocyanates within the scope of the present invention also include polymeric isocyanates made by reacting a polyol or amine with excess polyisocyanate. Method of Preparation of Preferred Embodiments To obtain a lubricating oil dispersant the cooligomer which consists of a number of C -C hydrocarbylsubstituted aliphatic dicarboxylic acid moieties connected by tert.-amide linkages is formed by contacting from 2:1 to 0.921 mol ratio of polysecondary amine to hydrocarbyl-substituted acid or acid generating compound such as the anhydride. Preferably, the amine will be present in excess, or slight excess, over the acid at a mol ratio of amine to acid of 21 :1. This cooligomer is subsequently reacted with a polyisocyanate. In a typical reaction, the secondary amine and the hydrocarbylsubstituted acid are contacted neat, or in a suitable solvent such as an aromatic solvent or hydrocarbon oil, at a temperature of from 100C to 200C with stirring for a period of from 1 to 100 hours. The product of this first reaction, which is the cooligomeric material, is reacted with polyisocyanate by contacting same at a temperature of from C to 250C for a period of from 0.1 to 24 hours, preferably from 0-200 C for from 0.5 to hours. The mol ratio of polyisocyanate to cooligomer is about 0.4l:1 or more. Generally, this mol ratio should be about 1:1 if the cooligomer is amineterminated at both ends. The molecular weight of cooligomer is determined, for example, by reaction with phenyl isocyanate or by well-known physical means. The final product may be used directly, or preferably is filtered and stripped under vacuum. The total cooligomer chain length depends upon the starting materials and the reaction conditions, but is believed to average from 2 to 25 succinic acid groups and a corre sponding number of di-secondary amine moieties under the stated conditions. The total molecular weight of the linked cooligomers depends chiefly on the number of carbon atoms in the hydrocarbyl substituent since this substituent can contain about 300 carbon atoms. If IR analysis shows the presence of unreacted isocyanate in the linked cooligomeric product, a subsequent reaction with a C -C low molecular weight amine such as an alkyl amine or alkylene polyamine may be carried out with 12 equivalents of amine, based on the number of free isocyanate groups determined from IR analysis, at 0-200C for 01-24 hours.

The following examples illustrate specific syntheses of some of the preferred embodiments of this invention. They are intended to be illustrative rather than exhaustive.

EXAMPLE 1 1,400 g of a 50 percent concentrate of polyisobutenyl succinic anhydride having an average molecular weight of about 1,000 (about 0.6 mol) was added to 700 g of a neutral petroleum oil of viscosity 100 SUS at 100F to make a 33 percent concentrate. The mixture was stirred until homogeneous and then 135.8 g about 0.7 mol) of tetramethyl triethylene tetramine was added and the mixture heated to 180C and stirred under nitrogen at 179-181C for 60 hours. The reaction product, weighing 2,044 g (38 percent concentrate) was reacted with toluene diisocyanate by charging 44.5 g of the diisocyanate at a dropwise rate to the cooligomeric product with stirring under nitrogen while heating. Diisocyanate addition was completed in about 15 minutes at which time the temperature of the reaction mixture was 40C. Heating of the reaction mixture to C continued for a total reaction time of 9 hours. IR analysis showed the presence of isocyanate groups.

EXAMPLE 2 The product of Example 1 was mixed with 2.7 ml (about 0.026 mol) of diethylamine and stirred at room temperature under nitrogen. The mixture was then heated to 70C over a period of 45 minutes and kept stirring under nitrogen at 7075C for 45 minutes. Additional amounts of diethylamine of 2.7 ml and 4.2 ml were added to the reaction mixture with continued heating and stirring at 42-49C for a total of 6 hours. Infrared spectra of the resultant product showed the isocyanate peak had almost disappeared. The product was placed under vacuum and heated to 120C for 1 hour. The product weighed 2,014 g (about 39 percent concentrate) and had an average molecular weight of about 7,000.

EXAMPLE 3 1,400 g of a 50 percent concentrate of polyisobutenyl succinic anhydride having an average molecular weight of about 1,000 0.6 mol) was mixed with 700 g of a SUS at 100F neutral petroleum oil to make a 33 percent concentrate. The mixture was stirred under nitrogen and heated to 50C with the addition of 136.0 g (about 0.7 mol) of tetramethyl triethylene tetramine. The reaction mixture was heated at l79185C under nitrogen for 47 hours. The reaction product which weighed 2,185 g was reacted with toluene diisocyanate by charging at a dropwise rate 48.0 g (about 0.27 mol) of toluene diisocyanate to the product while stirring under nitrogen and heating. The temperature was 52C when isocyanate addition was completed after 15 minutes. The reaction mixture was further heated to 75C and stirred under nitrogen a total of 8 hours. IR analysis showed the presence of isocyanate groups.

EXAMPLE 4 To the reaction product mixture of Example 3 was added 750 ml of hexane. The mixture was stirred until homogenous and then 20.2 g of diethylamine was added with stirring for 3 hours at room temperature. At that time the infrared spectra showed the isocyanate peak had vanished. The reaction product mixture was then stripped of hexanes and unreacted amine under vacuum at a temperature up to C. The reaction product weighed 2,258 g and had an average molecular weight of about 7,000.

EXAMPLE 5 The procedure of Example 3 was repeated up to a point prior to the reaction with isocyanate. The reaction product was found to weigh 2,209 g (about a 37 percent concentrate) and had an average molecular weight of about 4,000.

EXAMPLE 6 1,200 g of a 50 percent concentrate of polyisobutenyl succinic anhydride having an average molecular weight of about 1,000 was mixed with about 0.577 mol of ethylene dipiperazine in a 3-liter flask. The mixture was stirred at 170C for about 48 hours. The viscous product weighed 1,307.6 g and was diluted with 90 g of a 100 SUS at 100F neutral petroleum oil for further work.

EXAMPLE 7 1,085 g of the product of Example 6 (32 percent concentrate) was reacted with 8.3 g of toluene diisocyanate (about 0.048 mol) in 33.9 g of a 100 SUS neutral petroleum oil under nitrogen with stirring at 6064C. Infrared analysis showed the presence of unreacted isocyanate groups. 0.9 g of piperazine in 17.3 g of oil were reacted with the product at 60C.

EXAMPLE 8 1,024 g of the polyisobutenyl succinic anhydrideethylene dipiperazine coiiligomer of Example 6 was reacted with 6.2 g of toluene diisocyanate at 64C under nitrogen for a total of 19 hours. Infrared analysis showed little isocyanate absorption, but 0.25 g of diethyl amine was added to the product at room temperature while stirring for 30 minutes.

EXAMPLE A In other exemplifications, about 1 mol of a polypropenyl succinic anhydride having an average molecular weight of about 600 is mixed in 1,000 cc of benzene with 97 g (about 1.1 mol) of N,N- dimethylethylene diamine. The mixture is refluxed for 20 hours, whereupon 96 g of toluene diisocyanate is charged dropwise to the product with stirring. The mixture is kept stirring under nitrogen for 24 hours at 7080C. The product is stripped to yield the cooligomeric product.

EXAMPLE B The product of Example A, containing free (unreacted terminal) isocyanate groups, is diluted with 700 ml of hexane and contacted with 20 g of diethylamine at a temperature of 4050C for about 4 hours. Lubricating Compositions The compositions which find use in this invention contain oils of lubricating viscosity derived from petroleum or synthetic sources. The oils may be paraffmic, naphthenic,halogen-substituted hydrocarbons, asphaltic, or combinations thereof. Synthetic lubricating oils include hydrocarbon oils are polymerized and interpolymerized olefins, alkylbenzenes, polyphenols, alkylene oxide polymers and copolymers and derivatives thereof such as esters, ethers, etc. Silicon-based oils also form a useful class of synthetic lubricants. Carbox ylic acid esters such as octyladipate, nonylazelate, decylsuberate, butylalkenylsuccinate, etc.; also, inorganic esters such as phosphates and silicates form useful lubricating compositions.

Oils of lubricating viscosity normally have viscosities in the range of from 3550,000 Saybolt Universal Seconds (SUS) at 100F., more usually from about 5010,000 SUS at 100F.

The dispersants of the present invention may be prepared as concentrates having as high as weight percent of the dispersant in lubricating oil. Generally, concentrates will vary from about 10 to 80 weight percent of dispersant. However, when the oil is to be used in the engine, the amount of dispersant will generally vary from about 0.1 to 15 weight percent, more usually from about 0.25 to 5 weight percent. The lubricating oil compositions may therefore vary in the amount of dispersant from 0.1 to 80 weight percent.

Other additives may also be included in the lubricating oil. These additives include oxidation inhibitors, extreme pressure agents, pour point depressants, viscosity index improvers, antiwear agents, rust inhibitors, corrosion inhibitors, detergents and dispersants, etc. In general, the total amount of additives exclusive of the described dispersant will be in the range of from about 0.1 to 10 weight percent of the lubricating oil composition. In concentrates the weight percent of these addi' vssy lu al yb m biahe If advantageous, the lubricating composition can contain metallic salts, i.e., detergents exemplified by oilsoluble neutral salts and basic salts of alkali or alkaline earth metals with sulfonic acids,.carboxylic acid, phenols, etc. Basic salt designates metal salts wherein the metal is present in stoichiometrically larger amounts than the organic acid radical. These salts are prepared by methods described in the art, e.g., US. Pat. Nos. 3,488,284, 3,474,035, etc.

Evaluation V The isocyanate-linked cooligomeric dispersants were subjected to the severe Ford V8 Piston Varnish Test. In this test, a Ford V8 engine of 302 cu.-inch dislacement is cycled as idle/cold/hot at an rpm of 500/2500/2500 and water temperatures of 1 15/ 125/170F, and gallery temperatures of /175/205F for periods of 45/120/75 minutes. In the Piston Varnish test the engine is disassembled and piston varnish is measured on a scale of 010 with 10 being completely clean. In this test procedure, the engine is broken down at 20-hour intervals and piston varnish is measured at each stage.

A lubricating oil formulation was made containing 6 weight percent of dispersant (50 percent by weight concentrate) and 7.5 mM/kg of zinc dialkyl dithiophosphate, 7.5 mM/kg of zinc bis(polypropylene phenyl)- dithiophosphate, 30 mM/kg of overbased calcium sulfonate (11.4 percent calcium), and 30 mM/kg of carbonated, sulfurized, calcium propylene phenate (9.25 percent calcium) in a neutral petroleum oil. The results are given in Table l. The PIBSA/EDP/TDI dispersant additive is a toluene diisocyanate-linked cooligomer of polyisobutylene succinic anhydride and ethylene dipiperazine. The PIBSA/TEPA dispersant is a commercial dispersant produced by the reaction of polyisobutenyl succinic anhydride with the primary amino polyamine tetraethylene pentamine, which reaction, because of the presence of a primary amino group, leads to the production of polyisobutenyl succinimide. V

The polyisocyanate-linked cooligomers of polyisobutenyl succinic acid are compared in Table I with the well-known prior art dispersant, polyisobutenyl succinimide. The superior performance of the isocyanatelinked dispersants of the present invention over the prior art dispersant is evident at all stages of the experiment.

TABLE I Ford V-8 Piston Varnish Test Average of several runs Average molecular weight 16,000 Average molecular weight 14.000

The oxidative stability of these dispersants is demonstrated in the Oxidator B Test results of Table II. The Oxidator B Test is our laboratory designation for a test measuring resistance to oxidation by means of a Dornte-type oxygen absorption apparatus (R. W. Dornte Oxidation of White Oils, Industrial & Engineering Chemistry, Vol. 28, page 26, 1936). Normally, the conditions are 1 atmosphere of pure oxygen at 340F and one reports the hours to absorption of one liter of by 100 grams of oil. In the Oxidator B test a catalyst is used and a reference additive package is included in the oil. The catalyst is a mixture of soluble metal-naphthenates simulating the average metal anal ysis of used crankcase oils. Thus, the Oxidator B method measures the response to conventional inhibitors in a simulated application. The dispersants of Table 11 include the previously described co'ciligomeric products and PlBSA/TMT/TDl which is the toluene diisocyanate-linked coo'ligomer of polyisobutenyl succinic anhydride and tetramethyl triethylene tetramine. The compositions of Table 11 contain 3 percent of the oil-free dispersant, 1 percent of the commercial antioxidant di-tert.-butyl bis-phenol in a 496 SUS at 100F neutral petroleum oil. Table II shows the number of hours required to take up one liter of oxygen, the number of liters of oxygen taken up in hours of testing and the over-all change in viscosity at 100F. The remarkable superiority of the dispersant additives of the present invention over the known lubricating oil dispersant, polyisobutenyl succinimide, is amply demonstrated.

TABLE ll Hours/ Liters 0 Dispersant liter O 10 hours A Visc.

PlBSA/TEPA 2.9 8.7 197% PlBSA/TMT/TDI 2.1 8.4 102 PlBSA/EDP/TDI 4.0 6.5 86

TABLE 111 Ford V-8 Piston Varnish Tcst Hours: 40 80 100 120 PlBSA/TEPA/TDI 9.3 8.9 8.1 7.7 PlBSA/EDP/TDI 93* 90 8.) 8.5 PlBSA/TMT/TDI 9.7 9.0 8.7 8.8

Average of several runs The results clearly indicate the superiority in dispersancy of the toluene diisocyanate-linked products of polyisobutenyl succinic acid with polysecondary amines over the polyisocyanate-linked product of polyisobutenyl succinic acid with a polyamine contain' ing a primary amino nitrogen group. It is believed that the absence of a primary amino group in the polysecondary amine permits the formation of high molecular weight cooligomeric structures which when further linked by polyisocyanate are superior dispersants. The polyisobutenyl substituents in the above tests are de' rived from polyisobutenyl of 1,000 average molecular we h The test results amply illustrate the utility of the reaction products of the present invention as dispersants additives in lubricating oil compositions. Other reaction products formed from the specified reactants of the present invention also perform as superior lubricating oil additives; however, it is not possible to attempt a comprehensive catalog of such reactants or to describe the invention in terms of specific chemical names of such reactants and reaction products without producing a voluminous disclosure. One skilled in the art could, by following the teaching of the invention herein described, select the proper reactants and reaction conditions to provide a useful composition for his purpose. The invention lies in the preparation of polyisocyanate-linked cooligomers of a hydrocarbylsubstituted succinoyl compound and a polysecondary amine, and their use as dispersant additives in lubricating oil compositions.

1 claim:

1. A lubricating oil composition comprising a major amount of an oil of lubricating viscosity and in an amount sufficient to provide dispersancy:

the reaction product of an alkyl, aryl or alkaryl polyisocyanate with a cooligomer in a mol ratio of about 0.4-1 :1 at a temperature of about O200C',

2. A lubricating oil composition according to claim 1 wherein said polysecondary amine is a disecondary amine containing from 2 to 6 amino nitrogen atoms.

3. A lubricating oil composition according to claim 11 wherein said polyisocyanate is toluene diisocyanate.

4. A lubricating oil composition according to claim 1 wherein said hydrocarbyl substituent is polybutenyl or polypropenyl of from 30 to 300 carbon atoms.

5. A lubricating oil composition according to claim 1 wherein said polysecondary amine is selected from the group consisting of ethylene dipiperazine, tetramethyl triethylene tetramine, bis(N-piperazyl)propane,

trimethyl diethylene triamine, and piperazine. 

1. ALUBRICATING OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF AN OIL OF LUBRICATING VISCOSITY AND IN AN AMOUNT SUFFICIENT TO PROVIDE DISPERSANCY: THE REACTION PRODUCT OF AN ALKYL, ARYL OR ALKARYL POLYISOCYANATE WITH A COOLIGOMER IN A MOL RATION OF ABOUT 0.4-1:1 AT A TEMPERATURE OF ABOUT 0*-200*C; SAID COOLIGOMER IS THE REACTION PRODUCT OF A HYDROCARBYLSUBSTITUTED SUCCINIC ACID OR ANHYDRIDE, WHEREIN THE HYDROCARBYL GROUP CONTAINS AT LEAST 30 CARBON ATOMS, WITH A POLYSECONDARY HYDROCARBYL AMINE CONTAINING FROM 2 TO 12 AMINO NITROGEN ATOMS, NONE OF WHICH IS A PRIMARY AMINO NITROGEN ATOM AND AT LEAST TWO OF WHICH ARE SECONDARY AMINO NITROGEN ATOMS, IN A MOL RATIO OF ABOUT 1:1-2 AT A TEMPERATURE OF 100*-200*C.
 2. A lubricating oil composition according to claim 1 wherein said polysecondary amine is a disecondary amine containing from 2 to 6 amino nitrogen atoms.
 3. A lubricating oil composition according to claim 1 wherein said polyisocyanate is toluene diisocyanate.
 4. A lubricating oil composition according to claim 1 wherein said hydrocarbyl substituent is polybutenyl or polypropenyl of from 30 to 300 carbon atoms.
 5. A lubricating oil composition according to claim 1 wherein said polysecondary amine is selected from the group consisting of ethylene dipiPerazine, tetramethyl triethylene tetramine, bis(N-piperazyl)propane, trimethyl diethylene triamine, and piperazine. 